Marshmallow Catapult

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Blog entry by Lockwatcher posted 04-15-2011 12:43 PM 21601 reads 36 times favorited 7 comments Add to Favorites Watch

When I pulled this off of my cabinet, I did not expect so many would like to build these. Well, I took one apart so that we could make some notes – and then detail construction.

Below: The marshmallow catapult in it’s finished form.

As you can see below, the catapult concists of only 6 wooden parts & some miscellaneous hardware, all easy to build with handtools if need be. When we did this project with the scouts, we put it together as a kit that they could sand & assemble.

Below: The various parts of the catapult before assembly

The “main block” is 6” x 2.5” x 3/4” thick. One one end of the main block is a centered notch 1/4” wide by 3/4” deep. A hole is drilled 3/8” (from the notched end) so that the trim nail (trigger) will easily slide in and out.

Below: The main block with the slot cut in the end. A hand saw, bandsaw, or even a jigsaw could be used for this cut.

Above: The main block slot with the hole drilled for the finsih nail “trigger”

There are two “side blocks” they are 4.5” x 2.5” x 3/4” thick. Measuring from the bottom of each block (the short side), drill a 5/16” hole 1 5/8” from the bottom, 3/4” in from left side. This is the hole that holds the dowel for the pivot arm. Another hole is drilled at the top of each block. This hole is 21/64” to allow for a slightly loose fit. Measure from the top this time, 5/8” from the top & 1” in from the left side. On my unit, I made a second hole at 1 3/4” from the left side. This second hole allows you to adjust the stop position of the pivot arm.

Below: One of the two side blocks, in the correct orientation for the cutting information above (there is an extra hole in the lower right side that is not part of the project).

The pivot arm is 1” x 1” x 5.5” long. A 21/64” hole is drilled in one end of the pivot block – about a 1/2” in from one end of the block. A 1 1/4” forstner bit was used to make the “ammo holder”.

Below: The pivot arm cut from some Poplar scrap. You can use some clean pine for this or another piece of hardwood.

Above: Sand the bottom of the pivot arm into a nice curve (for clearence at the bottom). This curve could also be pre-cut on the bandsaw, scroll saw – or even a coping saw!

You will also need a length of 5/16” dowel rod. The bottom or pivot rod is 4” long. The other one is 5” long (the pivot stop).

Hardware needed: 1 1/4” finishing nails (4), 3” finishing nail (1), 1/2” plastic tubing – 2 3/8” long (should just fit over the dowel rod), small screw eye 1” long, rubber bands (experiment to find the right size).

Follow the pictures below for assembly:

Below: The short (4” long) dowel is lightly pressed into the lower hole. This will be tight as they are the same size.

Below: The pivot arm is slid onto the dowel. remember to position the pivot arm correctly.

Below: The other side is carefully pressed onto the dowel…just about ready to finsih assembly

Below: With a little glue added to the mating surface, the sides are nailed onto the main block using small finish nailes. You could even use drywall screws for this part (if using screws, predrill your holes).

Above: The sides are now hooked to the main block.

Below: The top dowel is slowly slid through the top hole as the tube is slid on. The tube needs to be there or the dowel will crack when firing your catapult.

Below: The dowel sticks out on both sides – this is important as this is what retains the rubber band.

Below: Lower the pivot arm down by the slot to determine the exact location for the screw eye (see how it is captured by the finsih nail).

Below: The finished catapult with the rubber band installed.

Above: Another view of the finished catapult.

Construction Note: This is an easy build. You can use almost any scrap lumber you have lying around. We had to build 12 of these for the scout group. Experiment to find the best rubber band to use – some will be too tight and break. Also the extra hole at the top will allow you to change the angle of the pivot stop. using the second position (towards the front) will also change the rubber band tension.

Please enjoy…if you do build one (or some) please post some pictures in the comment section!

Ken C.

-- Lockwatcher, Ohio,

7 comments so far

View Mickey Cassiba's profile

Mickey Cassiba

312 posts in 3545 days

#1 posted 04-15-2011 02:05 PM

Charlotte and the little dog both love marshmallows…I can have some fun with this…Thanks!!!

-- One of these hammers oughta fix that...

View TechRedneck's profile


770 posts in 3370 days

#2 posted 04-16-2011 12:06 AM

Thanks for taking the time to post this. This is a nice project for the grandson and I to work on.

-- Mike.... West Virginia. "Man is a tool using animal. Without tools he is nothing, with tools he is all.". T Carlyle

View Pathpounder's profile


98 posts in 4407 days

#3 posted 04-16-2011 01:29 PM

We have kid camp every summer for the grand kids where they build projects
. This is definitely on the list for this year.

View Jason's profile


660 posts in 4021 days

#4 posted 05-19-2011 06:24 PM

Thanks Ken. I built one of these Easter weekend. My boys loved it.

-- Jason - Colorado Springs

View MadeinGarage's profile


16 posts in 3202 days

#5 posted 05-20-2011 09:21 PM

Love this. I work with a group of Webelos and I know we’ll have fun hitting each other with marshmallows.

View Taff's profile


29 posts in 4049 days

#6 posted 05-24-2011 09:10 PM

A very simple and great set-up. I have just finished a trebuchet that throws unshelled peanuts for my grandson and was thinking of something for my granddaughter – I can imagine the battles those two are going to have. That’s what comes of being a vengful grandfather. My daughter will have some choice words for me. Thank you for posting with such detail

-- Glyn, North Carolina

View TechRedneck's profile


770 posts in 3370 days

#7 posted 05-25-2011 02:37 AM

Just keep an eye on the kids with the marshmallows… Make sure they don’t light them on fire and shoot them. That’s something I would have thought of back in the day! ( I’m much too mature and safety minded to do that now ; )

-- Mike.... West Virginia. "Man is a tool using animal. Without tools he is nothing, with tools he is all.". T Carlyle

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